Protective helmet



FIG. 1 is a front elevational view of a protective helmet showing our new design;

FIG. 2 is a perspective view thereof;

FIG. 3 is a left side elevational view thereof;

FIG. 4 is a top plan view thereof; and,

FIG. 5 is a rear elevational view thereof. 

The ornamental design for a protective helmet, as shown. 